ScreenBlind

Lock what others shouldn't see. Unlock what matters.

Selective multi-monitor lock screen for Windows. Cover the screens you choose — let the others keep showing what's on them.

Website · Download · Donate ❤

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What it does

ScreenBlind lets you lock individual monitors on a multi-display Windows setup. The locked screens go dark and require a password to wake — the unlocked ones stay visible and keep displaying their content, so a presentation, video, or dashboard can carry on while you step away. Mouse and keyboard input stays captured by the lock; the unlocked monitor is for viewing only, not interacting with.

Features

• 🖥️ Selective locking — pick exactly which monitors to lock
• 🔒 Password-protected — single password unlocks every locked screen at once
• 🐭 Cursor trapping — mouse can't escape onto unlocked monitors
• 🎨 Built-in screensavers — Bubbles, Matrix rain, or your own image slideshow
• 🕐 Roaming clock — clock and date drift to random positions to keep the lock surface alive
• 🌌 Animated background — dark hues slowly shift across the color wheel
• 🪶 Lightweight — single .exe, no installer, no background services, no telemetry
• 📦 System tray — runs quietly until you need it

Screenshots

Coming soon. If you'd like to contribute screenshots, see Contributing.

Installation

From release (recommended)

Grab the latest ScreenBlind.exe from the Releases page and run it. No installer, no admin rights required.

From source

git clone https://github.com/<your-fork>/ScreenBlind.git
cd ScreenBlind
pip install -r requirements.txt
python main.py

Tested on Python 3.11+ and Windows 10/11.

Build your own executable

.\build.bat

The standalone ScreenBlind.exe lands in dist/.

How it works

1. Monitors tab — check the screens you want to lock
2. Security tab — set a password (PBKDF2-SHA256, hashed locally)
3. Hit "Lock Now" — selected screens are covered by an overlay that:
   • Sits above the taskbar via SetWindowPos(HWND_TOPMOST)
   • Traps the cursor with ClipCursor so it can't reach unlocked screens
   • Blocks the Windows key from opening the Start menu via WH_KEYBOARD_LL
   • Shows a clock, date, and password prompt on key/mouse activity
   • Transitions to a screensaver after idle timeout
4. Unlock once — every locked screen wakes up simultaneously

Settings persist to %APPDATA%\ScreenBlind\settings.json. Passwords are stored as a base64-encoded salt + PBKDF2 key and never leave your machine.

Limitations — please read

ScreenBlind is a focus and privacy tool, not a replacement for the Windows lock screen. Two Windows shortcuts cannot be intercepted by any user-mode application:

Win+L still works

The Win+L shortcut is processed by win32k.sys at the kernel level, before it ever reaches user-mode keyboard hooks. No regular application can reliably block it (this includes ScreenBlind, AutoHotkey, and similar tools). Pressing it will show the standard Windows lock screen.

Ctrl+Alt+Del still works

Ctrl+Alt+Del is a hardware-level Secure Attention Sequence built into Windows specifically so no software can ever intercept it. This is intentional OS security and applies to every third-party lock tool.

What this means in practice

If someone presses Win+L or Ctrl+Alt+Del on a locked machine:

1. The Windows lock screen appears on top
2. Your Windows password is required to dismiss it
3. ScreenBlind's overlay is still active underneath
4. Your ScreenBlind password is then required to reveal the screens

So a bypass attempt actually adds a layer rather than removing one — the attacker now needs both passwords.

Other limitations

• Windows-only — built on Win32-specific APIs (cursor clipping, top-most enforcement, low-level keyboard hooks). macOS / Linux ports are wishlist.

Configuration

Setting	Where	Default
Locked screens	Monitors tab	(none)
Password	Security tab	(unset)
Idle → screensaver	Screensaver tab	120 seconds
Animation style	Screensaver tab	Bubbles
Slideshow folder	Screensaver tab	(none)
Slideshow interval	Screensaver tab	5 seconds

Stored as JSON in %APPDATA%\ScreenBlind\settings.json.

Project structure

ScreenBlind/
├── main.py              # Entry point + settings UI (Qt)
├── blind.py             # Per-screen overlay widget + BlindManager + Win32 helpers
├── animations.py        # Bubbles / Matrix / Slideshow screensavers
├── auth.py              # PBKDF2 password hash + verify
├── settings.py          # JSON load/save under %APPDATA%
├── generate_icon.py     # Programmatic icon generator
├── icon.ico             # App icon
├── media_assets/        # Logo + header artwork
├── build.bat            # PyInstaller build script
└── requirements.txt     # PyQt6

Support

ScreenBlind is free and will stay free. If it saves you from someone peeking at your monitor during a coffee run, consider supporting development.

☕ Donate via PayPal — any amount welcome.

Other free ways to help:

• ⭐ Star this repo
• 🐛 Open issues for bugs you find
• 🔁 Share it with anyone who uses multi-monitor setups

Contributing

Pull requests welcome — especially for:

• Screenshots / demo recordings for the README and landing page
• Additional screensaver animations
• macOS / Linux ports (probably a larger undertaking)
• Bug reports with reproduction steps

License

MIT © Hemi G

Free to use, modify, and distribute — including commercially. The only requirement is keeping the copyright notice. See LICENSE for the full text.

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screenblind.cc · Lock what others shouldn't see.